Adds namespaces storage limit SaaS feature

What does this MR do and why?

Adds namespaces storage limit SaaS feature

Introduces the SaaS-only namespace storage limit feature for use in controlling flow for the namespace storage limit feature (SaaS only).

This MR uses it to remove a single rubocop violation as the initial use-case for the feature, once the MR has merged we can address other similar violations

Refs #431340 (closed)

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